1. Field of the Invention
The present application relates to a method to activate or start an optical transmitter module that installs a semiconductor laser diode (LD), an LD driver, and a thermo-electric cooler (TEC) to control a temperature of the LD.
2. Related Background Arts
An optical transceiver usually provides an optical transmitter to transmit an optical signal and an optical receiver to receive another optical signal. The optical transmitter often installs a TEC to mount the LD thereon in order to set an oscillation wavelength of the LD and optical power output from the LD by maintaining a temperature of the LD in constant. The optical transceiver often installs other optical and electrical components. When the optical transceiver is powered on, or recovered from a power saving mode; a large current sometimes flows in the optical transceiver, which is often called as a rush current. In particular, when a difference between an ambient temperature and the target temperature of the LD is large, the rush current flowing in the TEC often becomes large. In order to reduce the rush current, one type of optical transceivers restricts a current flowing in the TEC depending on the current temperature of the LD and an ambient temperature in the optical transceiver.
An enhanced transmission speed and capacity by an optical transceiver with a small-sized package have been continuously requested in the field of the optical communication. Assembly density of an optical transceiver, and/or an optical transmitter is further increased, which inevitably makes a position of a driver to drive the LDs close enough to the TEC, or a driver is sometimes directly mounted on the TEC. In such an arrangement, heat generated by the driver affects the terminal stability of the TEC, and the rush current of the TEC becomes larger.